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Terms in this set (49)

-small-to-medium size theropods (Ornithomimosaurs especially), were most definitely fast runners (thigh bones are short compared to the length of the rest of the hind limb)
- the fastest theropods clocked at 40-60 km/h
- Reconstructed muscle mass and volume can also indicate speed of movement (this has been done for larger theropods) although they were still not the fastest
- evidence of swimming from a trackway in Spain ( the dinosaur swam with alternating movements of the two hind limbs, a pelvic paddle swimming motion - which is similar to those used by modern bipeds, including aquatic birds)

- dromaeosaurids and troodontids had especially sophisticated feet: the claw on digit II was huge, curved and sharp, and capable of a very large arc of motion (during normal walking and running it would have been held back or up, so as to protect it from damage) that claw would be brought forward as if spring-loaded and, with a powerful kicking motion of the leg, used to eviscerate the bellies of prey, perhaps disemboweling them in one stroke
- strong arms
- three-fingered hands (very dexterous) - the digits were long, capable of extreme extension, and tipped with powerful claws
- thumb (digit I) would fold across the palm in a semi-opposable way (could grasp and hold onto things)
- Maniraptorans had a specialized wristbone (a semi-lunate carpal) which allowed them to bend their hands at the wrist, back towards the bones of the arm
- large theropods such as Tyrannosaurus and Tarbosaurus, have very short arms (that can't reach their mouth), have bone structure in the arms that is stout and powerful, suggesting active use (suggested that the size of the skull of larger carnivores was so big that the upper limbs were reduced in size to balance out the weight. Larger front limbs would have made them too top/front heavy)
- the arms of Tyrannosaurus shows that the robust bones and large, stout claws at the tips of strong fingers could have lifted 300 kg, which is compelling evidence that they served some function.

- Skull: heads tend to be proportionately large, which is the case with carnivores in other animal groups as well.
The biggest head known in this group could be up to 1.75 m (5+ feet) in length
- the long and slender skulls as seen in Spinosaurus have a tendency to be rather primitive, looking not too different from the non-dinosaurian archosaur descendants
- more evolved have robust and deep-jawed skulls (ex - the powerful bite of the tyrannosaurids')
- Most of the theropods, even larger ones such as Carcharodontosaurus, had much more lightly built skulls than the Tyrannosaurids
- mechanics of defleshing can be compared to a falcon (slash and tear)

- tended to be flattened from side to side
- were recurved (curved backward)
- were pointed, and serrated
-The jaw joint in Theropods was at the level of the tooth row, so the jaws acted like scissors
- some had prominent serrations and narrow cross-sections, like hack-saw blades
- All ornithomimosaurs (except one primitive genus) lost all their teeth (small-skulled, long-legged, long-tailed theropods that look, somewhat, like ostriches, a beak with a ridged edge which is probably a shearing feature, skeletons have been preserved with gastroliths, so they no doubt relied on them to grind their food since their teeth wouldn't have done the job)
- Oviraptorosaurs were also toothless (skull was very short with pneumaticity (apparently), jaw musculature was very well developed, in the middle of the palate are a pair of stout, peg-like projections - used for crushing)
- Fossil Recovery: most cases they are isolated, individual skeletal remains, although there are rare instances of bone beds of a single theropod species

Senses: extremely important for a hunting lifestyle
- size of the olfactory bulb in Tyrannosaurus is huge (heightened sense of smell)
- Sharp vision was important for all theropods, and their eye size is large
- In Dromaeosaurids (including Deinonychus, and Velociraptor), and especially in the Troodontids, the eyes have migrated to a more forward position, giving overlapping fields of vision which would mean these animals saw stereoscopically
- narrow snouts of Tyrannosaurids allowed 55° of binocular vision, less than humans or owls, but still far more than hadrosaurs
-The middle ear cavities of both troodontids and ornithomimosaurs are greatly enlarged, such that they would have been very good at hearing low frequency sounds; in troodontids they would have been able to tell which direction the sound came from

- horizontal position of the vertebral column and the center of gravity being positioned near the hips gave theropods very good balance
- Deinonychus was aided by having its tail stiffened by elongate processes along the neural arches. It was flexible at its base only, directly behind the pelvis

- theropods = within bird range for intelligence (had more complex perceptual ability and more precise motor-sensory control than birds) This implies sophisticated inter- and intraspecific behavior

- theropods have been fossilized with remains in their stomachs of lizards, mammals, fish, and hadrosaur bones. Tyrannosaurus coprolites found have been 30-50% bones, including parts of a ceratopsian frill
- evidence of cannibalism from tooth marks (found on bones) as well as bones in the stomach of the same species of dinosaur

- seem to be social, gregarious animals
- horns or head crests in some therapods, which may have functioned, much as head ornamentation of hadrosaurs and ceratopsians, in social behavior/ritual display
- larger theropod skulls have slightly elevated upper margins on the snout, and/or raised and roughened bumps over the eyes ( believed to have been cores for hornlets (small horns) made of keratin) which could have also been used for head-butting (they are more developed in adults than in children)
- sexual dimorphism is found in two theropods, Syntarsus and Coelophysis (one morph has a long skull and neck, thick limbs, and powerfully developed muscles around the elbow and hip; the other form has a shorter skull and neck, and slender limbs. The larger, more robust form is thought to be the female)

-Brooding behavior is known in Oviraptorosaur, with adult skeletons found on top of nests of eggs with Oviraptorosaur embryos inside. A more recent find in Mongolia of this behavior was that of Gigantoraptor.
- a 10-15 fold increase in body size from hatchling stage to adult (growth is thought to be very rapid)
- probably k-strategists (cared for young)
- started out in minor numbers in the Early Jurassic, but by the Late Cretaceous, were dominant in a large part of the terrestrial ecosystems, particularly in the southern hemisphere and Europe
- reduction in the number of fingers, and strength, of the hands
- a variety of forms, including the toothless, and probably herbivorous, Chinese Limusaurus of the early Late Jurassic, and the Late Jurassic Elaphrosaurus. Along with several other genera these two are usually put into an "unofficial" group: the Elaphrosaurs
- toothed members of this group wouldn't have been able to bite and hold on to their prey, so would probably depended on cutting, or biting chunks out of their prey, weakening them by blood loss to their eventual death
- Neoceratosaurs have shorter and thicker necks than the primitive forms (two major groups within this clade, the Ceratosauridae and the Abelisauroidea)
- typified by Ceratosaurus, from the Late Jurassic of North America. This genus has members which vary from 6-8 meters in length
- Abelisauroidea: within are two clades, the Abelisauridae and the Noasauridae (tend to have elongated prongs on their vertebrae. The Noasauridae are smaller and slender, typified by Noasaurus from the Late Cretaceous of Argentina) also includes the Majungasaurus from Madagascar. This group is typified by tiny arms, which in some members couldn't even bend at the elbow as the ulna and radius were reduced to the size of wrist bones (carpels). Their legs were usually shorter, and stockier, than in other Ceratosauria.
- The Abelisaurids had a tendency to have a lot of horny, (keratin sheathed?) texture on their skull (as seen in Majungasaurus) and their snouts had a tendency to be shorter, and rounded, with short, thickened teeth.
- The Abelisauridae were the top predators of the Late Cretaceous on the land masses of India, Madagascar, South America, and Europe. Larger, later forms haven't been found on Australia, Antarctica, or continental Africa, at least not yet
- Composgnathids: small predatory maniraptors known from localities in Eurasia and South America which are Late Jurassic to Early Cretaceous in age. Their neck & legs are long, and the tail especially so. The thumb and first finger of the 3 fingered hand were stout and strong. Their skulls were very light due to the enlarged eye orbit and skull fenestrae
(could find pigment color thanks to fossilized melanosomes - pigment bearing organelles)

- Alvarezsaurids: ranges in age from the Late Jurassic to the end of the dinosaur era. Had unusual skeletal characteristics: teeth were small, numerous, stout and semi-tubular. Arms were very short but very powerfully muscled (the hand made of one, massive funtional finger with large claw - function not understood but possibly used for tearing apart termite mounds). The public bone of the pelvis is retroverted (pointing backwards like Ornithischians).

- Therizinosaurs: range in size from small to large, and lived during the Cretaceous in the Northern Hemisphere. They are thought by many to be herbivores, unusual for a theropod. These are highly evolved mantiraptoran theropods, and the larger and more heavily built species have been compared to giant ground sloths. They had small heads and long necks, but unlike them the Therizinosauria had extremely elongated and powerful claws on their front limbs. Large guts, Short legs, long necks and beaks, and built their nests in colonies to protect from predators.

- Oviraptorosaurs: Small to large, flying (according to some analyses) and flightless herbivorous or omnivorous maniraptorans, of Cretaceous age; known only from the Northern Hemisphere. The head is not large compared to the body size, and the skulls are typically short and deep. Teeth are reduced or absent. Neck is proportionately long. Tail is short. Both arms and legs vary in length in the different genera within this clade from long to short; arms have two or three fingers.
Archaeopoteryx exhibits diagnostic features of archosauria, and also the erect stance, and the modified ankle joint of a dinosaur.

It has hollow bones, a feature it and modern birds share with Theropods. It also has the enlarged 3 fingered hand that Theropods have.

Archaeopteryx has a furcular (wishbone), diagnostic of Tetanurans, and also has the elongate zygaphophyses which would have stiffened its tail.

It possesses the distinctive semi-lunate carpal, a shortened ischium, and large, circular orbits, diagnostic characters of the Coelurosaurs.

Archaeopteryx has a grasping, 3 fingered hand, like the maniraptorans, along with an elongation of the middle digit.

It has a highly reduced fibula, and forelimbs that are equal to or greater than the length of the hindlimbs, diagnostic of the Eumaniraptorans.

As in all avialans, Archaeopteryx has tail vertebrae which show an extensive elongation of the hemal and neural arches, and the teeth in their skull have lost their serrations.


Although the fingers in birds are fused, they are recognized as being the same three which are prevalent in the hands of Theropoda.

Pneumatic bones are hollow, and it would be easy to think that they evolved as an adaptation for lightness.

Pneumatic bones are present in several lineages of Saurischians, including the large sauropods with the pleurocoels in their vertebrae.

Obviously the sauropods couldn't fly, so pneumatic bones didn't evolve specifically for flight in birds as they were present in organisms long before the first actual bird appeared.
- Anchiornis is a small feathered eumaniraptoran dinosaur from a Late Jurassic (~155 my) age locality in Liaoning Province.
(We know the colors of the feathers in Anchiornis because of the preservation of the melanosomes within the feathers.)
- There is also a 124myo locality in Liaoning Province, China which has excellent preservation of generally complete and completely articulated animals. The fine mudstones show the impressions of the animals' coverings and also some dark staining, probably the original organic matter.
The first discovered organism from that locality is Sinosauropteryx, a small coelurosaur which did not have the proper skeletal design to be able to fly. It was covered in barb-like filaments.
- Also at that locality was the somewhat larger, toothless Caudipteryx, an oviraptosaur.

There was a very large, ostrich-sized, therizinosaurid named Beipiaosaurus, which also would not have been able to fly. This animal has primitive feathers with only barbules.

The elongated, single filament feathers of Beipiaosaurus are very apparent on the photo of the fossil.

Sinornithosaurus, a non-flying deinonychosaur, had feathers that in every way are comparable to those of modern birds.

The development of feathers coincides with the development of tetanuran dinosaurs.

More basal tetanurans, such as the coelurosaurs have basal types of feathers. More derived tetanurans, like the eumaniraptorans, bear more derived feathers.

We also have evidence of the connection between theropods and birds through studies of soft tissue.

In 2006, organic soft tissue was obtained from a Tyrannosaurus femur. The molecular composition of one of the proteins therein, collagen, more closely matched those of a living chicken than any other living animal.
- Stance- All non-avian dinosaurs had erect stance (all modern creatures with erect stances are endotherms - the controlled temperature is necessary for the musculature to remain in an erect stance)
- Buccal pumping (in organisms with sprawling stance because the weight shifts from one side to the other so only one lung can inflate at a time) vs using both lungs (more volume = better locomotion)
- Limb anatomy, inferred activity levels (longer strides = more efficient: higher levels of activity for a longer period of time before entering an anaerobic physical state), and calculated walking and running speeds (height to hip, stride length)
- Assorted adaptations for processing large volumes of food (secondary plate for chewing)
- Hearts: # of chambers = 4 (2 distinct circulatory systems: one for the lungs (pulmonary), and the second for the rest of the body (systemic circuit))
- Minds: Intelligence (higher in endotherms due to metabolism providing more neuromuscular control) Air movement and water loss (The lungs must be able to replenish the system with fresh air quickly for endothermy to be present. That would lead to water loss unless systems are in place to prevent it. Modern mammals have respiratory turbinates (conchae) in the nasal cavities, convoluted sheets of delicate tissue-covered bone. These moisture covered surfaces pull water out of the exhalant air before it exits our bodies) many dinosaurs have olfactory turbinates that would aid their sense of smell, but none are known to have respiratory turbinates
- Histology: Bone growth Timing of growth from egg to adult
Haversian bone is bone growth done by "remodeling" older bone (dissolution of primary bone and redeposition of secondary bone).
That secondary bone is redeposited in Haversian (vascular) canals (middle of nested cylinders), and resorption/redeposition can be done repeatedly during growth.
Eventually, dense, secondary Haversian bone is formed. That type of bone is found in birds and mammals.
Secondary Haversian canals are known to be correlated with:
-size and age, and even possibly with the type of bone being replaced
-the amount of mechanical stress undergone by the bone
-nutrient turnover (the metabolic interaction between developing bony tissue and soft tissue)

Bone growth was very rapid (more like birds than modern reptiles)
"bolide" = a large meteor that explodes in the atmosphere

- Some geologists feel that these flood basalts (and the hot spot) occurred due to an impact of an extraterrestrial body with the Earth at that geographic locality (evidence: the Shiva Crater in the ocean crust off the SW coast of India)
-Impacts (which would throw up enormous quantities of dust) could, in theory, cause global cooling by blocking out sunlight.
- several other (smaller) craters of around the same age as Chicxulub and the larger Shiva have been discovered, all between latitudes 20°N and 70°N. Examples include the Silverpit crater in the United Kingdom, and the Boltysh crater in Ukraine, both of which are much smaller than Chicxulub but likely to have been caused by objects many tens of meters across striking the earth ( could be explained by a much larger object which broke up into multiple parts upon contact with the earth's gravity well and atmosphere)
-In the mid-1970's, geologists investigating the K/T (Cretaceous/Tertiary) boundary in Italy discovered a spike in the amount of Iridium within the layer, many times what would normally be found. The element Iridium is found in large quantity in meteorites and can also be added to surface sediments by unusually high volcanic activity. When a bolide of major size hits Earth, a good portion of that object would be vaporized into dust upon impact, spreading the resulting dust high into the atmosphere and thus around the entire planet
-Shocked Quartz- When a large object "rings the earth's bell", quartz grains in rocks of the nearby region will develop parallel fractures due to the "shock" of the impact. Shocked quartz was found in rocks surrounding the Gulf of Mexico, especially to the northwest
- Tektites- Small globules of "frozen" rock (glass) that form when the heat of the incoming bolide vaporizes itself and part of the earth's crust are found in the sediments in proximity to the impact site. Tektites were found in sediments surrounding the Gulf of Mexico and strung out to the Northwest as far as Colorado
-Soot layer- Heat of impact starts massive wildfires in surrounding terrain, leaving behind a soot layer in the sediment. Anything that falls through the atmosphere will heat up due to the friction of its passage. A recent example of this occurred in early 2013 in Russia when a meteor (estimated at 20 meters in length) entered the atmosphere at a low angle of trajectory.
- Any such impact which occurred in the ocean would cause a major tsunami. There is evidence of tsunami waves on the shorelines surrounding the Gulf of Mexico
- 10 km meteoroid left a 100 km crater
- Some of the cenotes of the Yucatan position seem to line up along the "fracture" zone that developed around the perimeter of the crater. Mapping the gravity anomalies of the Yucatan also reveal differences in a bull's-eye pattern (Cenotes are deep holes in Limestone bedrock which form due to the dissolution of the bedrock by groundwater along fracture zones)